The invention allows the local and quasi-instantaneous measurement of a speed vector of an ionizable gas flow in its plane of measurement. In addition, it permits the determination of the vorticity (the local and temporal variation of the speed vector of flow), which was difficult, if not impossible, to achieve with previous devices.
The invention brings into play the creation of ions in the gas flow by the corona effect, and the measurement of the influence of the said speed vector on the movement of these ions.
There are several existing apparatus for measuring the gas flow, in fact of a component of the latter, bringing into play the ions produced by the corona effect. These apparatus are divided into two classes:
the class of apparatus in which the jet of ions is perpendicular to the speed of flow, in which the beam of ions is displaced to a greater or lesser degree from a first collecting electrode to a second collecting electrode, the source of ions and the two collecting electrodes (placed side by side) being arranged on either side of the jet which serves to measure the speed; and
the class of apparatus in which the jet of ions is parallel to the speed of flow, making use of grilles of which one emits the ions and the other or others collect ions, the flow of gas passing successively through these parallel grilles; by way of example, it is possible to cite the French Pat. No. 2.250.981 filed on the 13th of November 1973 by Monsieur Jean Zizine.
In the aforementioned two classes of apparatus, the measurement of the average speed of a flow is achieved, namely the flow which passes between the source of ions and the collecting electrodes in the apparatus with the jet of ions perpendicular to the flow or that which passes through the grilles in the apparatus with the jet of ions parallel to the flow.